1. Technical Field
The present invention relates to a printed circuit board and a method for manufacturing the same, and more particularly relates to a printed circuit board having a connection terminal which has a structure preferable to connect with a connector, and a method for manufacturing the same.
2. Description of the Related Art
Recently, demands for downsizing electronics are increasing, and the same demands are also increasing for a printed circuit board attached to the electronics. In general, a printed circuit board has a main body and a connection terminal. On the main body, a circuit layer is disposed for connections of various electronic parts. The connection terminal is engaged and connected with an external connector.
The printed circuit board has various types such as a Rigid Printed Circuit board (RPC), Flexible Printed Circuit board (FPC), RPC/FPC composite board, Flexible Flat Cable (FFC) or the like. Here, the FFC is a cable only for connection, which does not have the aforementioned circuit layer. However, the FFC can be regarded as a kind of the printed circuit board because it is composed of a tape-shaped or ribbon-shaped flexible insulating board and lead wiring layers printed parallel thereon.
On the other hand, the connector is an electronic part to connect the connection terminal of a printed circuit board with electronics, a trunk connection cord or the like. The connector has also been reduced in height (thickness) thereof along with downsizing of the electronics and printed circuit boards.
When the printed circuit board is used in an apparatus having a movable portion such as a hinge (e.g. a foldable cellular phone and the like), at lease a part of the printed circuit board corresponding to the movable portion is composed of the FPC or FFC. In this case, the printed circuit board likely has a connection terminal formed along one of the outlines of FPC or FFC for connection of a connector.
The connection terminal of printed circuit board is more likely to be thinner along with reduction of the height of the connector. In such circumstances, the connection terminal is required to maintain an adequate mechanical strength and shape even in many insertions into and removals from the connector to obtain a good electrical connection and secure engagement with a contact portion of a connector terminal in the connector.
Therefore, an example of a general structure of a conventional connection terminal provided in a printed circuit board will be described with reference to FIG. 1. This figure is a sectional view schematically showing a connector and a connection terminal of the printed circuit board connecting with the connector.
The connector C0 has a connector case Ca (depicted by two-dots chain lines) and a plurality of connector terminals C1 housed in the connector case Ca. The connector case Ca is made of, for example, plastic. The connector terminals C1 are arrayed in the case Ca with a parallel relationship. Each terminal C1 is made of conductive and elastic metal plate, and molded to have a U-shape with two arms. Each connector terminal C1 has a protruding contact portion C2 formed so as to protrude from at least one of inner surfaces of the two arms.
A connection terminal T is connected with a main body of a printed circuit board PC. The connection terminal T is formed into a rectangular plate, and has a flexible insulating board 51 integrally connecting with the main body and a plurality of lead wiring layers 53 provided on an upper surface of the flexible insulating board 51. The lead wiring layers 53 are formed by patterning a copper film adhered on the upper surface of the flexible insulating board 51 by a adhesive layer 52 provided therebetween. The patterned lead wiring layers 53 are arranged parallel to each other on the flexible insulating board 51.
A main body side of each lead wiring layer 53 is covered with a coverlay 55 adhered by an adhesive layer 54. A connector C0 side of each lead wiring layer 53 is exposed from the coverlay 55 so as to form a lead terminal layer 53a at the tip-end portion thereof.
In the connection terminal T, a reinforcement layer 57 is adhered on a lower surface of the insulating layer 51 by an adhesive layer 56 provided therebetween. End surfaces of the insulating layer 51, lead terminal layers 53a and reinforcement layer 57 are terminated so as to form a common end surface Te which forms one of outlines of the printed circuit board PC.
In the above conventional technique, the lead terminal layers 53a is likely to be peeled off from the insulating board 51 when the connection terminal T is inserted into and engaged with the connector C0. This is because an end surface of the lead terminal layer 53a, which is located on the common end surface Te, is formed so as to be normal to an insertion direction, thus the end surface is likely to butt an edge of an inner surface of the connector terminal C1 or a protruding portion of the terminal portion C2.
Accordingly, there are problems in that the contact portion C2 of the connector terminal C1 cannot properly engage with the upper surface of the lead terminal layer 53a to electrically connect therewith, and in that the adjacent terminal layers unexpectedly create a short circuit by bending peeled terminal layers 53a. 
The engagement state between the connection terminal T and connector C0 is expected to be stable for a long time. However, since the connection terminal T may be inserted into and removed from the connector C0 in many times, the connection terminal T may be peeled off, making the connection between the connection terminal T and the connector C0 impossible.
A Japanese Patent No. 3248266 (patent document 1) discloses a technique to prevent peeling off of the connection terminal. This technique will be described with reference to FIG. 1. As seen in this figure, the connector case Ca has tapered inner surfaces Cat. The patent document 1 intends to solve a problem that the lead terminal layer 53a and insulating substrate 51 are peeled off by contact of ends of the lead terminal layers 53a with the inner surfaces Cat before the insertion of the connection terminal T into the connector C0 is completed.
As a solution for the above problem, a projection portion PX (indicated by dash lines) is provided at the ends of reinforcement body 57 and insulating substrate 51. This projection portion PX protrudes longer than the extension of the end surface of the lead terminal layer 53a toward the insertion direction. However, it is still impossible to solve the above problems resulting from the lead terminal layer 53a butting the edge of the inner surface of the connector terminal C1 or the protruding contact portion C2.
Meanwhile, the common end surface Te along the outline of the printed circuit board PC is formed by a conventional technique (see the Japanese Patent No. 2923012 (Patent Document 2)). In this technique, a printed circuit board base material having the same circuit patterns thereon is separated by cutting (punching) into each printed circuit board having the circuit and outlines to form the final shapes.